The water temperature from 1980 to 2000 and the anchovy catch from 1990 to 2000 in the southeastern portion of the South Sea of Korea were used to illustrate the influence of water temperature on the catch of the anchovy, Engraulis japonica. 1993 and 1998 were selected as poor and good fishing years therefore, the horizontal and vertical distribution of water temperature and catch per unit effort in these years was compared. When the anchovy catch was lower, the water temperature at 10 m was also about $0-2^{circ}C$ lower than during a normal year, which resulted in the formation of a weak thermocline. Conversely, when the anchovy catch was higher, the water temperature at 10m was $0-2^{circ}C$ greater than during a normal year, which resulted in the formation of a strong thermocline at around 20 m.